Thermal interface material and semiconductor device incorporating the same

ABSTRACT

A semiconductor device includes a heat source, a heat-dissipating component for dissipating heat generated by the heat source, and thermal interface material filled in a space formed between the heat source and the heat-dissipating component. The thermal interface material includes 50% to 90% in weight of at least one metal powders having an average particle size of 2 to 20 μm and selected from the group consisting of spherical tin powders and powders of memory alloy, and 5% to 15% in weight of silicone oil having a viscosity from 50 tO 50,000 cs at 25° C.

1. FIELD OF THE INVENTION

The present invention relates to a thermal interface material which isinterposable between a heat-generating electronic component and a heatdissipating component; the present invention also relates to asemiconductor device using such a thermal interface material.

2. DESCRIPTION OF RELATED ART

With the fast development of the electronic industry, advancedelectronic components such as CPUs (central processing units) are beingmade to have ever quicker operating speeds. During operation of theadvanced electronic components, a larger amount of heat is generated. Inorder to ensure good performance and reliability of the electroniccomponents, the operational temperature of the electronic componentsmust be kept within a predetermined range. Generally, a heat dissipatingapparatus such as a heat sink or a heat spreader is attached to asurface of the electronic component, so that the generated heat isdissipated from the electronic component to ambient air via the heatdissipating apparatus. However, the contact surfaces between the heatdissipating apparatus and the electronic component are rough andtherefore are separated from each other by a layer of interstitial air,no mater how precisely the heat dissipating apparatus and the electroniccomponent are brought into contact; thus, the interface thermalresistance is relatively high. A thermal interface material is preferredfor being applied to the contact surfaces to eliminate the airinterstices between the heat dissipating apparatus and the electroniccomponent in order to improve heat dissipation.

The thermal interface material includes base oil and fillers filled inthe base oil. Thereinto, the base oil is used for filling the airinterstices to achieve an intimate contact between the heat dissipatingapparatus and the electronic component, whilst the fillers are used forimprove the heat conductivity of the thermal interface material tothereby increase the heat dissipation efficiency of the heat dissipatingapparatus. Therefore, the fillers having high heat conductivities arethe preferred choice in improving the heat conductivity of the thermalinterface material.

SUMMARY OF THE INVENTION

The present invention relates to a thermal interface material forelectronic products and a semiconductor device using the thermalinterface material. According to a preferred embodiment of the presentinvention, the semiconductor device includes a heat-generatingelectronic component, a heat-dissipating component for dissipating heatgenerated by the electronic component, and a thermal interface materialfilled in a space formed between the electronic component and theheat-dissipating component. The thermal interface material includes 50%to 90% in weight of metal powders having an average particle size of 2to 20 μm and selected from the group consisting of spherical tin powdersand powders of memory alloy, and 5% to 15% in weight of silicone oilhaving a viscosity from 50 tO 50,000 cs at 25° C.

Other advantages and novel features of the present invention will becomemore apparent from the following detailed description of preferredembodiment when taken in conjunction with the accompanying drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present thermal interface material can be betterunderstood with reference to the following drawings. The components inthe drawings are not necessarily drawn to scale, the emphasis insteadbeing placed upon clearly illustrating the principles of the presentthermal interface material. Moreover, in the drawings, like referencenumerals designate corresponding parts throughout the several views.

FIG. 1 is an assembled view of a semiconductor device according to apreferred embodiment of the present invention;

FIG. 2 is an explanatory view of a thermal interface material of thepresent invention, showing a normal state of the thermal interfacematerial; and

FIG. 3 is an explanatory view of the thermal interface material of FIG.2, showing an operation state of the thermal interface material when itis disposed between an electronic component and a heat-dissipatingcomponent and is urged by the heat-dissipating component towards theelectronic component under a pressure.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an electronic device 10 includes an electroniccomponent 12, such as a central processing unit (CPU) of a computerdisposed on a circuit board 11, wherein the electronic component 12 is aheat source of the electronic device 10. The electronic device 10further includes a heat-dissipating component 13 for dissipating heatgenerated by the electronic component 12, and a thermal interfacematerial 14 filled in a space formed between the electronic component 12and the heat-dissipating component 13. The electronic component 12 needsto be cooled. The heat-dissipating component 13 is a heat sink, whichincludes a base 131 and a plurality of fins 133 disposed on the base131. The heat-dissipating component 13 is attached to the circuit board11 via a resilient fixing member 15, which can be deformed to provide aresilient force in clamping the heat-dissipating component 13 onto theelectronic component 12. The fixing member 15 clamps the base 131 of theheat-dissipating component 13 and the circuit board 11 together, therebyurging the base 131 downwardly towards the electronic component 12 viathe resilient force exerted by the fixing member 15. The thermalinterface material 14 is pressed by the heat-dissipating component 13,thus filling entirely the space formed between the electronic component12 and a bottom face of the base 131 of the heat-dissipating component13.

The thermal interface material 14 is a silicone grease compositionhaving high thermal conductivity, and includes a base oil 141 and anamount of fillers 143 filled in the base oil 141.

The base oil 141 is 5% to 15% in weight of the thermal interfacematerial 14; that is, the base oil 141 has a weight which is no lessthan 5% and no more than 15% of a weight of the thermal interfacematerial 14. The base oil 141 is silicon oil which has a viscosity inthe range of 50 to 50,000 cs at 25° C. The major component of thesilicon oil is organopolysiloxanes, whose formula is RaSiO(4-a)/2.Alternatively, the silicon oil may be organopolysilalkylenes,organopolysilanes, or copolymers. In the formula, R presents hydrocarbongroup, which polymerizes with siloxanes to acquire correspondingorganopolysiloxane, such as dimethylpolysiloxane, diethylpolysiloxane,methylphenylpolysiloxane, dimethylsiloxane-diphenylsiloxane copolymersor alkyl-modified methylpolysiloxane. In this embodiment, theorganopolysiloxane is dimethylpolysiloxane, which is the major componentof the dimethyl silicone oil. Alternatively, the R may present aminogroup, polyether group or epoxy group in the formula.

The fillers 143 are 50% to 90% in weight of the thermal interfacematerial 14; that is, the fillers 143 have a weight which is no lessthan 50% and no more than 90% of the weight of the thermal interfacematerial 14. The fillers 143 are selected from the group consisting ofspherical tin powders and powders of memory alloy, such asNi—nickel-titanium) alloy or Co—Zn—Al (cobalt-zinc-aluminum) alloy,which are easily to change their shape into a specific shape under apressure or a raised temperature. Alternatively, the powders of thememory alloy may be a mixture of the Ni—Ti powders and the Co—Zn—Alpowders. An average particle size of the fillers 143 is in the range of2 to 20 um. When the fillers 143 are the mixture of the spherical tinpowders and the powders of memory alloy, the ratio of the spherical tinpowders to the powders of memory powder is in a range of 1:1 to 1:10 inweight.

The thermal interface material 14 further includes no more than 35% inweight of oxide powders (not shown) having an average particle size of0.1 to 5 um and selected from the group consisting of zinc oxide andalumina powders. Alternatively, there may be no oxide powder filled inthe base oil 141.

Particularly referring to FIG. 2, the fillers 143 of the thermalinterface material 14 are substantially sphere-shaped in a normal state.In this state, the fillers 143 of the thermal interface material 14 areevenly distributed in the base oil 141 and space a distance from eachother. The fillers 143 of the thermal interface material 14 do not haveintimate contacts with each other. Referring to FIG. 3, when theheat-dissipating component 13 is disposed on the electronic component12, the round-shaped fillers 143 of the thermal interface material 14filled in the space between the electronic component 12 and theheat-dissipating component 13 are under pressure, whereby they changetheir shape to be ellipse-shaped fillers 143 a. The ellipse-shapedfillers 143 a of the thermal interface material 14 intimately contactwith each other with increased area. Therefore, the thermal conductivityof the thermal interface material 14 is increased, and the heatgenerated by electronic component 12 can be easily transmitted to theheat-dissipating component 13 to be dissipated via the thermal interfacematerial 14. Hereinafter, experimental data is provided to validate sucha result.

Table 1 below shows heat resistances of thermal interface materials withdifferent fillers. The weights of these thermal interface materials arethe same, i.e., 50 g, and the base oils of these thermal interfacematerials are dimethyl silicone oils having a viscosity of 10,000 cs at25° C. The table 1 shows that the heat resistance of the present thermalinterface material is lower than those of conventional thermal interfacematerials I and II. TABLE 1 Heat resistance Thermal interface Volume (°C. material Fillers % cm²/w) The present thermal Spherical tin powder 500.343 interface material having an average vol % particle size of 5.0 μmConventional thermal Alumina (Al₂O₃) powder 50 0.618 interface materialhaving an average vol % (I) particle size of 5.0 μm Conventional thermalZinc Oxide (ZnO) powder 30 0.860 interface material having an averagevol % (II) particle size of 0.4 μm

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size, and indicated by the broad general meaning of the terms in whichthe appended claims are expressed.

1. A thermal interface material comprising: 5% to 15% in weight of baseoil; and 50% to 90% in weight of fillers filled in the base oil, whereinthe fillers have an average particle size of 2 to 20 μm and are selectedfrom the group consisting of spherical tin powders and powders made ofmemory alloys.
 2. The thermal interface material as described in claim1, wherein the base oil has a viscosity from 50 to 50,000 cs at 25° C.3. The thermal interface material as described in claim 1, wherein thebase oil is silicone oil.
 4. The thermal interface material as describedin claim 3, wherein a major component of the silicone oil isorganopolysiloxane.
 5. The thermal interface material as described inclaim 4, wherein the organopolysiloxane is dimethylpolysiloxane.
 6. Thethermal interface material as described in claim 1, wherein the ratio ofthe spherical tin powders to the powders of memory alloy is in a rangeof 1:1 to 1:10 in weight.
 7. The thermal interface material as describedin claim 1, wherein the memory alloy is Ni—Ti alloy.
 8. The thermalinterface material as described in claim 1, wherein the memory alloy isCo—Zn13 Al alloy.
 9. The thermal interface material as described inclaim 1, further comprising 0% to 35% in weight of oxide powders. 10.The thermal interface material as described in claim 9, wherein anaverage particle size of the oxide powders is in the range of 0.1 to 5μm.
 11. The thermal interface material as described in claim 9, whereinthe oxide powders are selected from the group consisting of zinc oxideand alumina powders.
 12. A semiconductor device comprising: a heatsource; a heat-dissipating component for dissipating heat generated bythe heat source; and a thermal interface material filled in a spaceformed between the heat source and the heat-dissipating component, thethermal interface material comprising: 50% to 90% in weight of at leastone metal powders having an average particle size of 2 to 20 μm andselected from the group consisting of spherical tin powders and powdersmade of memory alloy; 5% to 15% in weight of silicone oil having aviscosity from 50 to 50,000 cs at 25° C.; and 0% to 35% in weight of atleast one oxide powders having an average particle size of 0.1 to 5 μmand selected from the group consisting of zinc oxide and aluminapowders.
 13. The semiconductor device as described in claim 12, whereinthe memory alloy is one of Ni—Ti alloy and Co—Zn—Al alloy.
 14. Thesemiconductor device as described in claim 12, wherein a major componentof the silicone oil is organopolysiloxane.
 15. The semiconductor deviceas described in claim 14, wherein the organopolysiloxane isdimethylpolysiloxane.
 16. The semiconductor device as described in claim12, wherein a ratio of the spherical tin powders to the powders ofmemory alloy is in a range of 1:1 to 1:10 in weight.
 17. A thermalinterface material adapted for being applied between a heat-generatingelectronic component and a heat-dissipating component, comprising: abase oil; and fillers filled in the base oil, wherein the fillerscomprise at least one of tin powders and powders of memory alloy. 18.The thermal interface material as described in claim 17, wherein the tinpowders and the powders of memory alloy each have a spherical shapebefore the thermal interface material is applied between theheat-generating electronic component and the heat-dissipating component.19. The thermal interface material as described in claim 18, wherein thetin powders and powders of memory alloy each have an elliptical shapeafter the thermal interface material is applied between theheat-generating electronic component and the heat-dissipating component.20. The thermal interface material as described in claim 19, wherein thefillers further comprise oxide powders.